THE  DISEASE  AS  FOUND  IN  THE  FIELD. 

THE  LEAF-SPOT  DISEASE  OF  TOMATO 


BY 

G.  H.  COONS  AND  EZRA  LEVIN 


This  disease  caused  a 'practical  failure  of  the  tomato  crop  in  1915.  It  may  he  expected  to 
he  serious  whenever  the  season  is  moderately  wet.  It  is  probably  the  worst  disease  of  the 
tomato.  This  bulletin  discusses  the  cause  of  the  disease  and  gives  practical  recommendations 


IAL  BULLETIN  No.  81. 


IKE  LUMMY 

OF  THE 

IJRIYERIITY  OF  IIUOMS 


JUNE.  1917 


Michigan  Agricultural  College 


EXPERIMENT  STATION 


BOTANICAL  DEPARTMENT 


for  control. 


^ * 


EAST  LANSING 
1917 


Digitized  by  the  Internet  Archive 
in  2017  with  funding  from 

University  of  Illinois  Urbana-Champaign  Alternates 


https://archive.org/details/leafspotdiseaseoOOcoon 


551. Z 
C.'JZt 

c^p.3 


CONCISE  DIRECTIONS  FOR  CONTROL. 

It  is  definitely  known  that  seedlings  commonly  carry  the  The  disease 
infection  to  the  field.  The  seed  is  not  thought  to  carry  the  to  theHeid 
fungous  spores.  Therefore,  if  the  soil  in  the  flats  or  cold  seedlings, 
frame  is  clean  the  plants  start  clean.* 

* To  insure  clean  seedlings  spray  the  young  plants  at  least  sjvray  young 
twice  with  weak  Bordeaux  mixture  (2-2-50). 

t Do  not  follow  tomatoes  with  tomatoes.  Have  a system-  The  disease  is 
atic  rotation  for  your  fields.  Cleaning  up  of  trash  in  garden  Sverfromhve 
patches  and  fields  is  a good  sanitary  measure.  Do  not  throw  year 
old  vines  on  the  manure  pile  or  compost  heap.  diseased 

Where  the  type  of  culture  permits,  staking  of  tomatoes  The  spores 
will  largely  prevent  damage  from  tomato  leaf -spot.  Staked  theasoiifand 
tomatoes  give  greater  yields,  earlier  crops  and  allow  most  i^r leaves, 
efficient  spraying. 

After  the  plants  are  well  started  in  the  field,  spray  every  be 

10  days  with  Bordeaux  mixture  lf-^-50,  made  exactly  accord-  protected  by 
ing  to  directions.  Tlie  early  sprayings  are  most  important  m?xture!x 
in  preventing  the  disease  from  getting  a foothold.  When 
the  plants  are  large,  unless  the  application  is  thorough  it 
will  pay  to  spray  down  and  back  on  the  same  row.  This,  if 
a gentle  wind  is  blowing  and  if  the  sprayer  gives  a good 

* mist,  will  insure  a thorough  application. 

Tomato  leaves  make  a quick  growth.  Frequent  sprayings  payings  are 

* are  necessary  to  keep  the  new  growth  covered.  to  keep  the 

new  growth 
covered. 


*(1)  Soil  from  fields  which  have  not  recently  grown  tomatoes  is  safe  for  use.  Manure 
containing  tomato  trash  is  unsafe. 

(2)  Used  soil  may  be  sterilized  by  steaming  by  the  inverted  pan  method. 

(3)  Used  soil  may  be  disinfected  by  drenching*  with  formaldehyde  1 to  100  parts  water.  Use 
1 gallon  to  the  cubic  foot,  drenching  the  soil  completely.  A quart  of  solution  will  disinfect 
a flat.  Cover  with  paper  or  canvas  over  night.  Then  turn  the  soil  thoroughly  to  allow  the 
fumes  to  escape.  As  soon  as  the  soil  is  in  good  condition,  plantings  may  be  made.  This 
treatment  is  simple,  cheap  and  easy.  It  will  also  prevent  damping  off. 


52149 


Fig.  2. 


Diseased  plant  showing  the  killing  of  the  lower  leaves. 


INTRODUCTION* 


Michigan  is  one  of  the  great  tomato-growing  states.  The  Michigan 
crop  produced  amounts  to  nearly  a million  dollars  annually.  ^ worth  r°P 
Tomatoes  are  grown  for  ordinary  market  purposes,  for  can-  annually30 
ning  and  for  seed.  The  type  of  culture  and  the  varieties 
used  vary  with  the  utilization  of  the  crop.  The  methods 
used  in  growing  the  crop  influence  the  prevalence  of  this 
disease  to  a great  extent.  For  example,  it  is  found  that 
where  tomatoes  are  staked,  the  damage  from  leaf-spot  is 
greatly  reduced,  in  general,  seedlings  are  grown  in  green- 
houses or  cold  frames  and  set  by  hand  in  the  fields.  This 
method  of  procedure  lends  itself  readily  to  control  measures 
which  entirely  prevent  damage  from  the  leaf-spot  disease. 

THE  IMPORTANCE  OF  THE  LEAF-SrOT  DISEASE. 

The  leaf-spot  disease  of  tomato,  commonly  called  by  grow-  The  leaf  spot 
ers  “blight,”  caused  a practical  failure  of  the  crop  in  many  slnous™081 
localities  in  1915,  and  for  the  preceding  five  years,  has  ma-  ^ease^of^ 
terially  shortened  each  growing  season.  This  condition  is 
found  in  every  state  where  tomatoes  are  grown  commercially. 

The  consensus  of  opinion  of  pathologists  from  all  parts  of  the 
United  States,  is  that  the  Septoria  leaf-spot  is  the  most 
serious  disease  of  the  tomato. 

The  disease  has  been  found  in  the  northern,  as  well  as  the  The  disease 
southern  parts  of  Michigan.  Its  distribution  is  probably  as  spread  as  ~to- 
great  as  tomato  culture.  mat0  culture. 

HOW  TO  TELL  THE  DISEASE. 

The  signs  of  the  leaf-spot  disease  are  well  expressed  by  the  Leaf  spot 
common  name  “blight.”  The  growers  notice  a general  un-  bUghting  of  a 
thriftiness  in  the  plants  along  with  a blight  which  begins  on  {J^the8 
the  lower  leaves  and  which  gradually  advances  upward  on  bottom 
the  plant.  (Fig.  2.)  Blighted  leaves  if  carefully  examined  up'vard 
are  seen  to  be  covered  with  small  circular  spots,  commonly 
less  than  % of  an  inch  in  diameter.  In  some  cases  a whole 
leaflet  may  be  involved.  These  spots  are  sometimes  black, 
but  are  usually  grayish  with  a black  border.  (Frontispiece.) 

As  the  disease  progresses  the  spots  dry  and  the  leaflets  turn 

*This  popular  bulletin  is  based  on  Technical  Bulletin  25  of  this  Station.  Anyone  interested 
in  the  more  detailed  account  may  secure  the  technical  bulletin  so  long  as  the  supply  lasts. 

Those  who  make  request,  may  be  placed  upon  the  mailing  list  to  receive  bulletins  from  the 
College. 


6 


EXPERIMENT  STATION  BULLETIN. 


Spots  appear 
on  the  leaf- 
lets. Then 
the  leaves 
die,  falling 
from  the 
plant  at  the 
least  jar. 


The  leaves 
manufacture 
sugar  and 
starch.  The 
leaf  spot 
disease 
destroys  the 
factories. 


yellow.  The  leaves  die  and  drop  from  the  plant  at  the 
slightest  jar.  The  disease  advances  up  the  plant,  and 
soon  all  leaves,  except  a small  tuft  at  the  end  fall  from  the 
stem.  The  dropping  of  the  leaves  exposes  the  fruit,  which 
may  sunburn  badly. 

Spots  are  also  formed  on  the  calyx  and  stem  but  rarely 
on  the  fruit. 

The  damage  to  the  crop  comes  largely  from  the  loss  of  the 
leaf  surface.  The  leaves  of  plants  are  the  manufacturing 
organs  which  produce  the  starch  and  sugars  which  make  up 
the  greater  part  of  the  solid  matter  of  the  fruit.  A leaf  dis- 
ease interferes  with  the  manufacturing  power,  hence,  the 


Fig.  3.  Diseased  spots  magnified  five  times. 


Small,  sour, 
watery 
tomaloes  are 
caused  by 
leaf  spot. 


fruit  grows  slowly  or  not  at  all.  Half-matured  fruit  fails 
to  ripen.  The  crop  from  plants  with  blighted  foliage  is 
small,  sour  and  watery.  This  last  condition  is  often  com- 
plained of  by  canners ; although  they  ascribe  “watery” 
tomatoes  to  a wet  season,  rather  than  to  a fungous  disease 
made  severe  by  the  season.  In  short,  all  the  general  signs 
are  those  which  go  with  disturbance  of  food  manufacture  by 
the  leaves. 


THE  CAUSE  OF  LEAF-SPOT. 


a fungus  Leaf-spot  of  tomato  is  caused  by  a parasitic  fungus  called 

thlftomato  Septoria  ly coper sici  which  grows  and  feeds  in  the  tomato 
plant.  leaf.  A parasitic  fungus  is  a microscopic  plant  which  makes 


THE  LEAF-SPOT  DISEASE  OF  TOMATO. 


7 


no  food  for  itself  but  which  steals  its  living  from  another 
plant.  If  a diseased  spot  is  examined  with  a microscope, 
the  leaf  tissue  is  found  to  be  pierced  by  minute  threads. 

These  threads  are  the  body  of  the  fungous  parasite.  After 
the  threads  have  gro,wn  in  the  leaf  and  occupied  considerable 
area,  small  black  dots  appear  on  both  the  upper  and  lower 
surfaces.  (Fig.  3.) 

The  small  black  dots  are  hollow  spherical  cases  Needie- 
whicli  contain  countless  long  needle-shaped  bodies  called  areffe spores 
spores.  (Fig.  4.)  These  spores  are  to  the  fungus  what 
seeds  are  to  the  higher  plants.  A spore  washed  to  a tomato  parasitic 
leaf  and  given  favorable  temperature  and  moisture  will  fungus' 


Fig.  4.  Thin  section  of  spore  case,  showing  long  needle-shaped  spores.  Magnified  800  times. 

sprout  and  enter  the  leaf,  quite  as  a seed  sprouts  and  grows, 
only  the  soil  the  fungus  uses  is  the  leaf  tissue. 

The  spores  of  this  fungus  have  a jelly-like  coat  and  when  The  spores 
a diseased  leaf  is  wet,  the  spores  swell  and  push  out  of  the  onawetbout 
spore  cases  in  sticky  masses.  When  the  spores  are  once  out-  leaves*  or 
side  the  spore  case  they  float  apart  in  the  water  on  the  leaf 
and  frequently  sprout  and  enter,  thus  making  the  spot  larger 
or  causing  new  ones. 

The  spores  from  a diseased  leaf  may  be  washed  or  splashed  Rains  splash 
from  leaf  to  leaf  during  rains,  or  if  the  plants  are  worked  about*0168 
when  wet,  may  be  carried  from  plant  to  plant  on  the  culti- 
vator or  on  the  clothes  of  the  worker. 

The  spores  can  endure  at  least  three  days  drying,  hence,  cuiuvatmg 
those  which  wash  to  the  ground  may  be  dried  on  the  dust  spreads^he 
and  blown  about,  thus  leading  to  a wider  distribution  of  the  p^antstorom 
disease  in  the  field  or  from  field  to  field.  plant. 


8 


EXPERIMENT  STATION  BULLETIN. 


How  the 
spore  attacks 
the  tomato 
leaf. 


In  13  days 
one  spore 
produces 
thousands  of 
similar  spores. 


Either  the 
upper  or 
lower  surface 
may  be  the 
point  of 
entry. 


The  fungus 
lives  over  on 
old  trash 
from  last 
year’s 
diseased 
plants. 


The  weather 
does  not 
cause  the  leaf 
spot  disease. 


If  a spore  is  put  under  proper  conditions  it  will  begin  to 
sprout  in  about  twenty -four  hours.  The  sprouts  are  threads 
which  push  out  from  the  needle-like  spore.  In  a few  hours 
after  sprouting  the  thread-like  tube  enters  the  breathing  pore 
of  the  leaf.  Then  the  fungus  grows  in  the  tissues  of  the 
plant,  twining  among  the  cells.  In  about  six  days  after  the 
spore  reaches  the  leaf,  the  first  watery  discoloration  produced 
by  the  fungus  can  be  seen.  In  less  than  ten  days  the  spot 
is  definite  and  the  killing  of  the  invaded  leaf  tissue  is  com- 
pleted. The  fungus  fruits  in  about  13  days  and  produces 
several  black  spore  cases.  Hence,  one  spore  gives  rise  to 
countless  thousands  of  other  spores,  each  capable  of  repeat- 
ing this  story. 

If  the  lower  surface  is  the  point  of  entry  the  spots  are 
large  and  may  involve  one-half  or  the  whole  of  a leaflet.  If 
the  upper  surface  is  the  point  of  entry  the  spots  may  be  no 
larger  than  the  head  of  a pin.  Usually  the  upper  leaves  show 
this  latter  type  of  infection,  evidently  from  dust  as  a source. 
The  lower  leaves  are  infected  from  beneath,  doubtless  by 
splashings  from  the  ground  or  from  the  older  leaves. 

The  fungus  lives  over  winter  on  the  trash  from  a preced- 
ing tomato  crop.  It  lives  over  in  the  greenhouses  or  cold 
frame  in  the  trash  from  seedlings  left  in  the  soil.  The  spores 
have  not  been  found  on  tomato  seed.  Hundreds  of  plants 
from  all  the  common  varieties  have  been  grown  in  clean  soil 
without  one  case  of  leaf-spot  appearing  spontaneously. 

The  spores  of  the  fungus  are  released  from  the  spore  case 
only  when  the  leaf  is  wet.  Heavy  dews  give  conditions 
which  allow  an  oozing  of  spores.  By  far  the  greatest  factor 
in  spreading  the  fungus  is  a washing,  splashing  rain.  There- 
fore, the  disease  is  most  serious  in  a rainy  season  such  as  that 
of  1915.  Many  growers  make  the  mistake  in  thinking  that 
the  tomato  disease  is  caused  by  the  weather,  while  the  truth 
is  that  the  disease  is  caused  by  a parasite  whose  spread  is 
favored  by  the  wet  conditions. 

Growers  must  adopt  measures  which  will  insure  a crop  in 
spite  of  the  weather. 


THE  LEAF-SPOT  DISEASE  OF  TOMATO. 


9 


HOW  TO  PREVENT  LOSS  FROM  TOMATO  LEAF-SPOT. 


Resistant  Varieties. 

In  an  experiment  with  more  than  50  of  the  leading  tomato 
varieties,  no  variety  was  found  strikingly  resistant  or  sus- 
ceptible. Many  varieties  are  vigorous  growers  and  continu- 
ally keep  ahead  of  the  leaf -spot  by  the  production  of  new 
foliage.  Dwarf  varieties  usually  suffer  more  damage  than 
the  ordinary  sorts. 

Before  other  control  measures  can  be  considered,  we  must 
recognize  the  following  observations  that  have  been  dealt 
with  above: 

1.  The  sources  of  infection  are  at  least  two:  the  green- 
house or  the  hotbed  and  the  diseased  trash  in  the  field. 

2.  Infection  results  from  inoculation  upon  the  upper  and 
lower  surfaces  of  the  leaf. 

3.  The  period  from  the  time  of  inoculation  to  spore  exuda- 
tion is  about  13  days. 

4.  Moisture  is  the  primary  agent  in  dissemination  of  the 
disease. 

5.  The  exudate  of  spores  is  in  the  form  of  a mucilaginous 
mass.  The  spores  are  always  transferred  by  some  external 
agency. 

6.  It  has  been  shown  that  the  fungus  will  not  grow  at 
85°  F.  and  will  not  revive  after  5 days  at  98°  F.  Since  such 
temperatures  are  frequently  reached  during  the  summer 
months,  the  heat  relation  must  be  taken  into  consideration 
as  a natural  means  of  checking  the  disease. 

The  most  important  control  measures  for  this  disease  are 
preventive.  Clean  seedlings  in  clean  soil,  if  reasonably 
isolated  remain  practically  free  from  the  disease. 

In  order  to  be  sure  that  the  seedlings  do  not  become  dis- 
eased at  the  start,  clean  soil  should  be  used  in  the  green- 
houses devoted  to  seedling  production.  The  soil  should  be 
fresh  or  sterilized.  The  seedlings  should  be  sprayed  as 
soon  as  their  height  above  ground  makes  it  practicable,  and 
again  before  being  transplanted  to  the  field.  For  this  a 
weak  Bordeaux  mixture  (2-2-50)  is  advised. 

Since  it  has  been  determined  that  wintered-over,  diseased 
vines  possess  spores  which  are  viable,  the  old  trash  must  be 
destroyed  as  far  as  possible.  Since,  however,  this  is  not 
practical  except  in  greenhouses  and  gardens,  rotation  is 
strongly  urged.  While  there  is  no  experimental  evidence  to 
demonstrate  the  value  of  rotation  as  a means  of  control, 
numerous  instances  have  been  noted  in  which  rotation  has 
been  successful  in  controlling  the  disease. 


No  resistant 
variety  is  as 
yet  found. 


Summary  of 
facts  about 
the  disease. 


Prevention 

methods 

necessary. 


Clean  soil. 


Destroy  old 
trash. 


10 


EXPERIMENT  STATION  BULLETIN. 


The  spores 
are  carried 
when  wet. 


Spray  with 
Bordeaux. 


Reasons  for 
failures  in 
control. 


How  to  spray. 


Spraying  has 
succeeded  in 
in  Michigan. 


Since  spores  are  released  from  the  spore  cases  when  wet 
the  plants  should  not  be  “worked”  until  the  plants  are  dry. 
Growers  have  reported  cases  where  cultivation  began  at 
a small  infected  patch  and  the  disease  was  carried  over 
the  entire  field,  and  that  in  less  than  three  weeks  the  entire 
field  was  spotted.  This  is  now  readily  explained.  In  green- 
house practice,  irrigation  should  replace  the  ordinary  use 
of  the  hose. 

After  transplanting  to  the  field,  spray  with  4-4-50 
Bordeaux  mixture  every  10  days.  As  has  been  shown,  the 
period  from  time  of  inoculation  to  spore  exudation  is  at 
least  13  days.  Allowing  this  leeway  for  differences  in  period 
of  infection,  it  would  seem  that  a spray  so  applied  would 
give  the  necessary  protection. 

The  greatest  part  of  and  the  strongest  infection  results 
from  inoculation  on  the  lower  surface  of  the  leaf.  There- 
fore, all  the  precautions  are  less  effective  if  the  plants  are 
allowed  to  run  at  will  over  the  ground.  The  spraying  of  the 
under  side  of  the  leaf  is  not  accomplished  unless  the  appli- 
cation is  thorough.  Failures  to  control  the  disease  by  spray- 
ing are  doubtless  due  to  lack  of  thoroughness  and  timeliness. 

Spraying  with  4-4-50  Bordeaux  mixture  in  the  fields 
where  tomatoes  are  staked  should  be  extremely  successful. 
In  this  state  spraying  will  not  be  most  effective  unless  the 
spray  reaches  the  lower  surface  of  the  leaves.  A sprayer 
such  as  is  used  for  potatoes,  with  two  side  nozzles  set  to 
shoot  upward  and  if  practical,  with  one  central  nozzle  to 
spray  downward  for  each  row  will,  under  high  pressure,  be 
most  efficient  in  Michigan  fields. 

Spraying  tomatoes  with  Bordeaux  is  a common  practice 
in  many  tomato-growing  centers.  Wherever  it  has  been  tried 
it  has  become  a fixed  part  of  the  culture  of  the  crop.  No 
grower  can  afford  to  risk  his  crop,  and  no  company  can  afford 
to  risk  its  acreage.  The  spraying  experiment  of  the  College 
in  1913  at  Plymouth  is  a good  example  of  what  may  be 
accomplished.  In  this  experiment  “the  plants  that  were 
sprayed  with  Bordeaux  mixture  four  times,  produced  12.5 
tons  per  acre  while  the  plants  that  were  not  sprayed  pro- 
duced 5.2  tons  per  acre.  The  first  spraying  was  made  about 
one  month  after  the  plants  were  set  in  the  field  and  fre- 
quently enough  afterward  to  protect  the  new  growth.” 
(Every  ten  days  or  two  weeks).* 

Copper  sulphate  (Bluestone  or  Blue  Vitriol)  is  a little 
more  expensive  this  year  than  formerly.  In  spite  of  the 
cost,  spraying  is  a crop  insurance  which  is  most  strongly 
to  be  advised. 


Eustace,  H.  J.,  Mich.  State  Board  of  Agriculture  Report  1914  :234. 


THE  LEAF-SPOT  DISEASE  OF  TOMATO. 


11 


THE  SPRAYER. 

Tlie  type  of  sprayer  depends  upon  the  acreage  and  method 
of  culture.  The  market  gardener  can  control  tomato  leaf- 
spot  with  a small  knapsack  or  hand  sprayer. 

Tomatoes  are  commonly  grown  in  fields  of  5 to  10  acres. 
For  fields  of  this  type  a horse-drawn  traction  sprayer  is  to 
be  advised.  However,  efficient  work  can  be  secured  by  means 
of  a handpower  barrel  pump  mounted  on  a truck.  This  is 
the  cheapest  form  suitable  for  field  conditions  and  may  be 
rigged  up  for  from  $25  to  $40. 

For  large  acreages  or  for  community  or  company  use,  a 
power  sprayer  is  the  best  investment.  Such  an  outfit  will  put 
the  Bordeaux  on  most  efficiently  and  will  give  the  maximum 
protection. 


Knapsack 
sprayer  for 
the  small 
grower. 

Horse-drawn 
traction 
sprayer  for 
the  ordinary 
field. 


The  sprayer 
for  large 
acreages. 


12 


EXPERIMENT  STATION  BULLETIN. 


ARRANGEMENT  OF  NOZZLES. 


Arrange  the  The  necessity  of  spraying  the  under  side  of  the  leaves 
spray6 upward,  makes  the  arrangement  of  nozzles  important.  The  accom- 
panying diagram  shows  the  arrangement  believed  to  be  most 
efficient. 


Fig.  5.  Arrangement  of  nozzles. 

With  such  a setting  of  nozzles  the  leaves  can  be  efficiently 
covered  without  repeating  the  spray  in  the  reverse  direc- 
tion. 

Any  spraying  outfit  can  be  adjusted  to  suit  the  needs  of 
the  crop,  by  use  of  a few  pipe  fittings.  The  accompanying 
diagram  suggests  a cheap,  easily  arranged  setting.  (Fig.  5.) 
hesf y oii  can  ^l)rayin&  worth  while  even  if  the  outfit  is  not  ideal,  or 
Abetter  than  the  nozzle  arrangement  perfect.  Given  good  Bordeaux, 
none  at  all.  thoroughness  of  application  with  pressure  enough  to  produce 
a mist,  and  the  investment  will  yield  good  returns. 


THE  LEAF-SPOT  DISEASE  OF  TOMATO. 


13 


THE  MAKING  OF  BORDEAUX. 

FOR  SMALL  ACREAGES. 

(1)  Saw  a 50-gallon  barrel  (vinegar  or  oil)  and  make  two 
25-gallon  tubs. 

(2)  Put  2 pounds  of  Bluestone  (called  Blue  Vitriol  or 
copper  sulphate)  in  a cloth  sack  and  hang  over  night  in  one- 
half  tub  of  water  (12%  gallons).  Bluestone  dissolves  slowly. 
Hang  it  the  night  before  so  that  the  sack  is  just  under  the 
surface  of  the  water. 


DIP  EQUAL  PARTS  FROM  1 
AND  Z INTO  3 


Fine  mesh  screen 
and  funnel  to  strain 
Bordeaux 


Use  this  mixture  at  once  in  sprayer 


Dprayer 


Fig.  6.  How  to  make  Bordeaux  mixture  for  small  acreages. 


(3)  Make  a lime  paste  by  slaking  2 pounds  of  fresh  stone 
lime  in  one-half  pail  of  water.  Stir  this  into  the  half  tub 
(12%  gallons)  of  cold  water.  Hydrated  lime  (comes  in 
sacks)  may  be  used.  Use  2%  to  3 pounds  of  hydrated.  Then 
follow  the  directions  in  the  picture.  This  method  will  make 
25  gallons  of  spray. 


14 


EXPERIMENT  STATION  BULLETIN. 


FOR  LARGE  ACREAGES. 


To  make  100-gallon  batches. 


Bordeaux 
4-4-50  or 
8-8-100 
formula. 


(1)  Secure  four  50-gallon  barrels. 

(2)  Fill  barrel  No.  1 half-full,  and  hang  25  pounds  of 
Bluestone  so  that  the  Bluestone  is  just  under  the  surface  of 
the  water.  This  makes  stock  Bluestone,  1 pound  to  the  gallon. 

(3)  Fill  barrel  No.  4 half-full  of  water  and  stir  25  pounds 
of  freshly  slaked  stone  lime  or  about  30  pounds  hydrated 
lime  in  it.  This  is  the  stock  lime  paste,  about  1 pound  to  the 
gallon. 

The  stock  solutions  will  make  300  gallons  of  spray.  They 
will  keep  if  covered. 

(4)  Take  8 gallons  stock  Bluestone  from  barrel  No.  1 and 
add  to  42  gallons  of  water  in  barrel  No.  3.  (That  is,  till  the 
barrel) . 


1 25 LB£  BLUE-\ 
STONE  IN  25 \ 
GALSL  WATER!) 


25LB5.ST0N£\ 
LIME  IN  25  ,|L 
^ALS/WATERiT 


I DILUTE |li 
[BLUESTONE 


LUTE  MI  LI 
0F;LlMEi 


ADO  8 GALS.  OF  STOCK  BLUESTONE 
FROM  0bl.  No.1To4£ 

GALS.  OF  WATER. 


ADD 8 GALS. OF  STOCK  LIME 
FROM  Obi.  No.4TO  4 2. 
GALS.  OF  WATER. 


Fig.  7.  How  to  make  Bordeaux  mixture  in  100  gallon  amounts. 


THE  LEAF-SPOT  DISEASE  OF  TOMATO. 


15 


(5)  Take  8 gallons  of  stock  lime  from  barrel  No.  4 and 
acid  to  42  gallons  of  water  in  barrel  No.  3. 

(6)  Run  these  materials  together  through  a strainer  into 
the  sprayer  tank.  The  combination  is  Bordeaux  mixture 
and  must  be  applied  at  once. 

If  the  spray  tank  holds  only  50  gallons  make  the  dilution  on  one-half  the  above  scale. 

The  first  batch  may  be  tested  with  litmus  paper  to  make  sure  that  there  is  lime  enough. 
If  blue  litmus  paper  turns  red,  add  more  lime.  With  good  fresh  lime  using  the  amounts 
given,  no  test  is  needed.  If  weather  conditions  prevent  the  using  of  a batch  of  Bordeaux, 
it  may  be  kept  for  a long  time  if  cane  sugar  is  added  at  the  rate  of  one-half  pound  to 
50  gallons. 


